How to Efficiently Configure Compiler Flags in Multi-Target CMake Projects?

Efficient Compiler Flag Configuration in Cross-Platform CMake Projects

Setting Compiler Options for Different Compilers and Configurations

To address your concerns about setting compiler options for different compilers and configurations, here's an updated and improved approach:

<code class="cmake">cmake_minimum_required(VERSION 3.15)

project(HelloWorld)

string(
    APPEND CXX_FLAGS
    "$<IF:$<CXX_COMPILER_ID:MSVC>,"
        "/W4;$<$<CONFIG:RELEASE>:/O2>,"
        "-Wall;-Wextra;-Werror;"
            "$<$<CONFIG:RELEASE>:-O3>"
            "$<$<CXX_COMPILER_ID:Clang>:-stdlib=libc++>"
    ">"
)

add_compile_options("${CXX_FLAGS}")

add_executable(HelloWorld "main.cpp")

target_compile_features(HelloWorld PUBLIC cxx_lambda_init_captures)</code>

Improvements:

• Uses the CMake generator expression syntax introduced in CMake 3.8, which is simpler and more concise.
• Takes advantage of the add_compile_options() function, which allows you to specify compiler options in a clear and readable manner.
• Removes the need to manually set CMAKE_CXX_FLAGS and similar variables.
• Specifies C features using target_compile_features() instead of explicitly setting the C standard.

Multi-Target CMake Projects

To address your desire for a multi-target project where each compiler and configuration has its own target, you can use the following approach:

<code class="cmake">cmake_minimum_required(VERSION 3.15)

project(HelloWorld)

set(COMPILERS MSVC Clang GNU)
set(CONFIGURATIONS Debug Release)

foreach(_compiler IN LISTS COMPILERS)
    foreach(_config IN LISTS CONFIGURATIONS)
        add_executable(HelloWorld_${_compiler}_${_config} "main.cpp")

        # Set compiler flags for this target
        target_compile_options(HelloWorld_${_compiler}_${_config} PUBLIC
            "$<IF:$<CXX_COMPILER_ID:${_compiler}>,"
                "/W4;$<$<CONFIG:${_config}>:/O2>,"
                "-Wall;-Wextra;-Werror;"
                    "$<$<CONFIG:${_config}>:-O3>"
                    "$<$<CXX_COMPILER_ID:Clang>:-stdlib=libc++>"
            ">"
        )

        # Set C++ feature requirements for this target
        target_compile_features(HelloWorld_${_compiler}_${_config} PUBLIC cxx_lambda_init_captures)
    endforeach()
endforeach()</code>

Improvements:

• Creates multiple targets with unique names based on the compiler and configuration combinations.
• Configures compiler flags and C features for each target separately.

Best Practices and Further Reading

Here are some additional resources that may be helpful:

• [CMake Tutorial: Multiple Targets](https://www.cmake.org/cmake-docs/latest/manual/cmake-tutorial/MultipleTargets.html)
• [CMake Packaging and Deployment Guide](https://cmake.org/cmake-docs/latest/manual/cmake-packaging.html#packaging-multiple-projects-in-a-single-project)

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